Manufacturers of food and beverage cans typically use pull-tab sealing and opening mechanism or stay-on tabs, in which a tab is used to tear off the can top (full aperture end) or designated part thereof for leaving an opening at the can top. In the pull tab mechanism the tab is removed from the can whereas in the stay-on tab the tab remains after the opening is revealed.
Other solutions involve press button mechanisms, in which a designated opening in the can upper face is sealed by using soft connection of the sealer to the opening rim requiring pressing the softly connected seal downwards towards the inner space of the can for opening thereof.
These solutions are vulnerable to unauthorized penetration to the inner cavity of the containers after filling and sealing thereof by the manufacturer and enable insertion of materials into the containers while covering any trace of the penetration. For example, in the case of the pull-tab or stay-on tab sealing the tab connects to the top of the container usually through a connecting stud and can be easily rotated around the stud axis revealing some of the upper surface exposed for injecting a material into the can or even replacing the liquid in the can with a different liquid and covering the area of the penetration hole by rotating the tab back to its position again. In this way the user of the can cannot see that the can was “treated” and might innocently use it for drinking or for eating the food content thereof.